The ability to accurately predict the effects of disease and treatment on an individuals ability to function relies entirely on our capacity to understand the complex process that transforms muscular effort into functional movements. The purpose of this project was to extend existing human movement analysis methodology by developing analytical techniques that can provide direct estimates of the influence muscular effort has on the movement of all joints, body segments, and overall functional movement task performance. A previous application of one technique to data from a group of normal walkers clearly indicated the muscles that cross the ankle joint are the primary contributors to normal walking performance. Clinical case studies involving patients with physical impairments continue to reveal a vast array of compensatory movement control strategies. The analytical techniques being developed under this protocol add significantly to the foundation of our ability to ultimately understand the influence of disease on function and to predict the on set of physical disability.